A FOSSCOMM talk on Openess in Astronomy

By grigoris | Filed in Astronomy

On the previous weekend (October 13-14, 2018) the 11th Free and Open Source Software Communities Meeting was held in Heraklion of Crete (Greece). This is the Greek conference of the communities that develop free and open source software (such as Mozilla, Fegora, etc.). Although the meeting focuses on programmers and students it is open to all parties with a strong interest in open processes including other areas beyond just the software, such as hardware, society, economy, etc. Starting in 2008, it has been organized in 6 different cities so far (but not in Heraklion!), gathering a few hundred participants each time.

With such a diverse and different audience we (myself, Antonis Manousakis, and Eva Ntormousi) thought that it would be a great opportunity to present our (relatively biased) collected experience of these processed and applications from the modern research in Astronomy. So the title and the corresponding abstract was:

“Examples of openess in Astronomy”

Grigoris Maravelias, Antonis Manousakis, Eva Ntormousi

Traditionally Astronomy is a collaborative science in the sense that many researchers collaborate to observe a phenomenon, and they share their observations for further analysis and interpretation. Building upon this tradition many observatories today make available their observations so that modern astronomers have access to large datasets. Additionally, the technological advance of the instruments allows the observation of the Universe almost at the entire electromagnetic spectrum, even at the very recently confirmed gravitational waves. Thus, the modern astronomers are not only required to understand the Astrophysics behind these huge datasets but often they are called to develop the own necessary tools to conduct their research. Given the knowledge and the vast volume of data available today the collaborations are, more than ever, vital (especially with the forthcoming large projects that are currently built, e.g. 30m telescopes). In the framework of modern Astronomy we are going to present successful examples of how open approach has been applied.

While presenting openess in Astronomy, during the Free and Open Source Software Community Meeting of 2018 in Heraklion, Greece.

While presenting openess in Astronomy, during the Free and Open Source Software Community Meeting of 2018 in Heraklion, Greece.

This particular talk is released under the CC-BY-SA license, so we are going to provide all necessary material along with the presentation. Although in Greek, most probably an english version will become also available in the future.

In Zickgraf et al. 1989 (A&A, 220, 206) there is a comment on the density of the disk around the supergiant LHA 115-S 18. In Table 1 they provide (following Waters 1986) the mean particle density at r=R* for a number of sources: 3.2 x 1012, 2.6 x 1012, 4.6 x 1012, 1.7 x 1012 cm-3 for sources S 18, S 12, S 134, and R 126, respectively. Having calculated a maximum disk radius of 300R*, they calculate a mean density of few 109 cm-3. These values are consistent with both estimates from IR emission and by McGregor et al. (1988), who independently found densities of about 109 cm-3 from the CO first overtone emission in S 12, S 134, and R 66.

Kick-off meeting at a new position!

By grigoris | Filed in Astronomy

Today it was my first day at the new job! It will be based at the Institute for Astronomy, Astrophysics, Space Applications and Remote Sensing (IAASARS) of the National Observatory of Athens (Greece).

I will be working with Alceste Bonanos, along with Ming Yang and Frank Tramper, in a project related to the “Episodic Mass Loss in Massive Stars: Key to Understanding the Explosive Early Universe” (ASSESS).

Although excited I am too tired to write something more now. But more will come in the future!

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XXXth General Assembly of IAU – week 1

By grigoris | Filed in Astronomy

The XXXth General Assembly of the IAU is held in Vienna, Austria, from Aug 20 to 31, 2018. The first week is finished now and tomorrow the second starts.

It is the biggest convention I have been so far with almost 3000 attendees, from all around the world literally. If I was to use only one world to describe it, ti would be “HUGE”! The Vienna International Center is great as it is neally easy to navigate and it can accommodate such an event. It is also very interesting and definitely uncommon to see exhibitors in astronomical conferences. You can find a large variety of booths from publishers, telescope/instrument companies, universities/telescopes/institutions advertising their projects, societies promoting their work, ESO and ESA, and an exhibition dedicated to the 100th anniversary of IAU. To all of these add the promotional stuff and gifts (from stickers to t-shirts and bags) and you get a rather different atmosphere sometimes.

A perspective of the exhibition.

A perspective of the exhibition.

The supernova - part of the 100th anniversary of the IAU.

The supernova – part of the 100th anniversary of the IAU.


LEGO models of some telescope facilities - part of the 100th anniversary of the IAU.

LEGO models of some telescope facilities – part of the 100th anniversary of the IAU.

Of course the main core is the various symposia and meetings. I came in Vienna on Tuesday (Aug 22) so as to take a look at the session on circumstellar environment around AGB stars (IAU Symposium 343: Why Galaxies Care About AGB Stars: A Continuing Challenge through Cosmic Time). Then, in the afternoon I went to the reception of the Focus Meeting 14: IAU’s role on global astronomy outreach, the latest challenges and bridging different communities, which was held at the Natural History Museum of Vienna. That was finally an amazing experience. Apart from getting to know fellow participants we got a free tour around the museum by its director. The museum exhibits an overwhelming collection, which represents only a small fraction of its collection (which is stored under the floors that are open to the public, and is accessible only to its scientists). On the next day (Thursday) the meeting took place, where I had an eposter representing the collective work we have done with the Hellenic Amateur Astronomy Association.

Then on Friday the Division G (Stars and Stellar Physics) Days, started, which I followed as much as possible, although I did tried to listen to other talks (the University of Vienna provided a very useful app to check the program and create your own agenda to easily follow whatever interests you most).

Another interesting week in starting tomorrow. I have a talk at the Division G Days and a poster contribution at the IAU Symposium 346: High-mass X-ray binaries: illuminating the passage from massive binaries to merging compact objects.

A fascinating comparison of what we knew in 1919 and in 2019 - Part of the 100th anniversary of the IAU.

A fascinating comparison of what we knew in 1919 and in 2019. It is amazing how our knowledge has advances. (Part of the 100th anniversary of the IAU.)

For a certain project I had created a number of photometric catalogs, each one corresponding to a specific observing field. I would like to construct the final (merged) one but for this I needed to add a unique source identifier at the beginning of each row. I decided to create a F#-**** tag for each source with “F#” corresponding to the field id and **** to a counter for each source per field. The final command was:

for i in {1,2,4,5,6,7,8,9,10,11,12,13,16};do echo F$i.matches.all.cat;awk -v id="$i" 'FNR>1 {print "F"id"-"1+c++, $0}' F$i.matches.all.cat >> results.tmp; done

So the command reads all the specific numbers for which a catalog with a filename of F*.matches.all.cat exists. The number of each field ($i) is parsed as an external variable (id) to awk which places it as the unique identifier “Fid-counter” with the incremental “counter” (1+c++) corresponding actually to the number of row (1+counter to begin from 1 instead of 0 – FNR avoids the first line of each catalog which is a column description). All results are written appended to the output file results.tmp (created automatically when non-existing).

Then, we can use sed to add the header:

sed -i '1i\#SourceID ...' results.tmp

An amazing drawing of Saturn

By grigoris | Filed in Astronomy

In the era of imaging even from our cell phones making a drawing of a planet seems redundant. However, this is certainly a different perspective of a direct experience at the eyepiece of a telescope. And the final result can be fascinating, such as this drawing from Paul G. Abel, using the Clark telescope (a 24″ refractor) at Lowell observatory.

A drawing of Saturn using the 24" Clark refractor at Lowell observatory (Paul G. Abel).

A drawing of Saturn using the 24″ Clark refractor at Lowell observatory (Paul G. Abel).

Source: ALPO-Japan

Building an observatory in Syria

By grigoris | Filed in Astronomy

At the last issue of CAP journal (No. 23, Feb 2018) we find the article “The World at a Glance: Highlights from IAU National Outreach Contacts” that provides short news from the IAU National Outreach Contacts. And for Syria we read:

“Mohamad AlAssiry: Despite the political situation, the Syrian Astronomical Association was building an observatory and opened in August 2017.”

which I found impressive given the country’s situation since the war broke out in 2011.

Of course, a counter-argument would criticize the prioritization given the number of lives threaten everyday in Syria. However, only education and civilization will help us overcome (on the long-term unfortunately…) these problems.

Finally, after some years of work, it has been accepted for publication in MNRAS.

Resolving the kinematics of the disks around Galactic B[e] supergiants

Grigoris Maravelias, Michaela Kraus, Lydia S. Cidale, Marcelo Borges Fernandes, Maria L. Arias, Michel Curé, Georgios Vasilopoulos

B[e] Supergiants are luminous evolved massive stars. The mass-loss during this phase creates a complex circumstellar environment with atomic, molecular, and dusty regions usually found in rings or disk-like structures. For a better comprehension of the mechanisms behind the formation of these rings, detailed knowledge about their structure and dynamics is essential. To address that, we obtained high-resolution optical and near-infrared spectra for 8 selected Galactic B[e] Supergiants, for which CO emission has been detected. Assuming Keplerian rotation for the disk, we combine the kinematics obtained from the CO bands in the near-IR with those obtained by fitting the forbidden emission [OI] λ5577, [OI] λλ6300,6363, and [CaII] λλ7291,7323 lines in the optical to probe the disk structure. We find that the emission originates from multiple ring structures around all B[e] Supergiants, with each one of them displaying a unique combination of rings regardless of whether the object is part of a binary system. The confirmed binaries display spectroscopic variations of their line intensities and profiles as well as photometric variability, whereas the ring structures around the single stars are stable.

arXiv.org: 1807.00796

Figure 12 from the paper: A cartoon illustration of the disk-structures as derived from our analysis. We represent the [OI] λ5577 line as *[OI]*, the [OI] λλ6300, 6363 doublet as [OI], and the [CaII] λλ7291, 7323 as [CaII]. The arrows above the rings symbolize the typical ring-widths and are given in km/s. (For more details on the data used and references see Table 3. Note that the relative structures and sizes are not in scale.

Catching a supernova just before it happens

By grigoris | Filed in Astronomy

Victor Buso is a really very lucky man! On September 20, 2016 we wanted to test his new camera mounted on a 40-cm Newtonian telescope. He pointed to the spiral galaxy NGC 613 because it was at that time located near the zenith. He took a series of 20s exposures spanning approximately an hour and a half. During the first part (about 40 exposures) there was no sign of anything unusual. After a break of 45 min though the exposures that he took revealed the rise of a supernova (SN 2016gkg). He is the first person to ever achieve that, ie. to capture the rise of a supernova just before its maximum light!

These observations are an unprecedented set of data for supernova physics. According to the recent paper by Bersten et al (incl. Buso) 2018 the data shows the clear presence of the shock breakout phase in the optical, i.e. the phase associated with the propagation of the radiation shock inside the star and its dissolution at the surface (Waxman & Katz 2016). This lasts seconds to a fraction of an hour typically, unless there is enough circumstellar mater ejected from the progenitor star before the supernova explosion then this phase may extend to days. The phase produces bright X-ray/UV flash but its optical manifestation has not been observed. So these observations show that the optical light curve is characterized by an extremely rapid brightening at relatively low luminosity.

What I find very critical in this work is actually how quick-witted Buso was. He is an amateur astronomer that didn’t just take the images. Instead he properly reduced them and he noticed the difference. The next important step was to communicate this to the appropriate channels that allowed for follow-up observations to be obtained in in less than a day later (including Swift X-ray, UV and optical telescopes, see Bersten et al 2018 for a list).

References
Bersten et al, 2018, Nature, 554, 497 (NASA/ADS link)
Waxman & Katz, 2016, arXiv:1607.01293 (arXiv link)

Skinakas return!

By grigoris | Filed in Astronomy

Yesterday was the first night that I found myself at Skinakas Observatory. Even though some years have passed, there are really minor changes. The mountain welcomed us with great weather (scarce clouds, humidity close to 50%, and almost no wind at all!), while the seeing proved to be really good (~1″).

The 1.3m Skinakas telescope.